Linear Calcium Carbonate Chains by Directional Control of Ionic Bonding

As a result of the non-directionality of ionic bonds, oppositely charged ions always assemble into closely packed clusters or crystals rather than linear structured ionic species. Here, we generated a series of linear calcium carbonate chains, (Ca2+CO32-)n, with an orientated directionality of the ionic interactions. The formation of these ionic chains with long-range ordered ionic interactions was originally induced by the dipole orientation of the ions and subsequently preserved by capping agents. According to the appropriately established folding-capping model, rational control of the capping effect can regulate the length of the (Ca2+CO32-)n chain within 100 nm, corresponding to n ≤ 250. Our discovery overturns the current understanding of ionic bonding in chemistry and opens a way to control the assembly of inorganic ions at molecular scale, pushing forward a fusion of molecular compounds and ionic compounds that share similar topological control.